quoted

And I suspect that XFS swidth/sunit settings will still work
with RAID-10 parameters even over plain LVM logical volume on
top of that RAID 10, while the settings would be more tricky
when used with interleaved LVM logical volume on top of
several RAID-1 pairs (LVM interleaving uses LE/PE-sized
stripes, IIRC).

Stripe alignment is only relevant for parity RAID types, as it
is meant to minimize read-modify-write. There is no RMW problem
with RAID0, RAID1 or combinations. But there is a case for
'sunit'/'swidth' with single flash based SSDs as they do have a
RMW-like issue with erase blocks. In other cases whether they
are of benefit is rather questionable.

One would use a linear concatenation and drive parallelism
with XFS allocation groups, i.e. for a 24 drive chassis you'd
setup an mdraid or lvm linear array of 12 RAID1 pairs and
format with something like: $ mkfs.xfs -d agcount=24 [device]
As long as one's workload writes files relatively evenly
across 24 or more directories, one receives fantastic
concurrency/parallelism, in this case 24 concurrent
transactions, 2 to each mirror pair.

That to me sounds a bit too fragile ; RAID0 is almost always
preferable to "concat", even with AG multiplication, and I would
be avoiding LVM more than avoiding MD.